Electric switch



Nov. 11, 1924. 1,515,032

T. T. GREENWOOD ELECTRIC SWITCH Filed Oct. 29, 1920 2 Shoots-Sheet 1 25 1,79" J 20 fizz/en 2'07,

Nov. 11, 1924. 1,515,032

T. T. GREENWOOD ELECTRIC SWITCH Filed Oct. 29, 1920 2 Shuts-Sheet 2 Patented Nov. 11, 1924.

UNIT D STATES PATENT orrlca.

TALIA T. GREENWOOD, 0F TEMPLETON, MASSACHUSETTS, ASSIGNOB, BY KESNE AB- SIGNIENTS, TO CON'DIT ELMTBICAL MANUFACTURING COMPANY, A CORPORATION 01' IASSAOHUSETTS.

ELECTRIC SWITCH.

Application fled Oetober :0, mo.- Serialllo. 420,505.

To all whom it may concern:

Be it known that I, TALMA T. Gammwoon, a citizen of the United States residing at Templeton, in the county of Worcester and State of Massachusetts have invented an Improvement in Electric witches, of which the following is a specification.

This invention relates to oil immersed electric switches especially adapted to carry high values of current; and has for its object generally to improve the construction and operation of a switch of the t e set forth and, specifically, to increase t e current-carr ing and current-interrupting capacity o the'switch.

The current carryin capacit of an oil immersed electric switc depen s upon the temperature of the switch components and, especially, the oil in which the switch members are immersed. In practice the current carrying capacityof the switch is limited by the rise in temperature of the oil and, other things being equal, the switch in which the oil is maintained at the lowest temperature will carry the greatest value of current. The current interrupting capacity of the switch is also affected by the temperature and usually a switch having a relatively high oil temperature can not safely interrupt as high a value of current as can a switch havin a relatively low oil temperature.

The oil receptacle of the switch, especially in switches adapted to carry and, interrupt current of relatively high value, is rovided with an insulating lining of wood or the equivalent which is interposed between the switch members and the heat dissipating wall of the receptacle to prevent contact of the are formed upon circuit interruption with the metal of the receptacle. The lining extends over the bottom and upwardly along the side walls of the receptacle to a point above the oil level, although in some cases it may not extend entirely to the surface of the oil. The lining is usually in direct contact with the side walls of the receptacle and is, intact, a box which fits within the oil rece tacle. 1 I

T e ex osed outer surface of the side walls of e receptacle provide practically the sole means by which heat ma be disslpated from the oil in the rece tac e. Inasmuch as the linin covers the side walls, the oil cannot come in 'rect contact with the side walls and, consequently, can not dissipate its heat. The lining servesas a heat insulator as well as an electrical insulator. While the material composing the lining may be more or less porous, especially if the material is wood, and so may become saturated with oil, yet the heat given u to the side walls of the receptacle is negligi 1e, as no effective cir'cu- I lation of oil can take place.

Some linings arespaced from the side walls of the oil receptacle and the space therebetween contains oil but there is no provision for efiective circulation of oil from the space within the lining past the side walls and, consequently, there is no substantial dissipation of heat.

In some instances, the level of oil may extend above the top of the linin and thereby be in direct contact with the si e walls of the oil receptacle. In this case some heat may be dissipated from the oil but, here again, the arrangement of the lining is such as to prevent effective circulation of the-oil for the dissipation of its heat to keep down the temperature of the oil.

In carryin out my invention, I rovide an electrical y insulating lining t e side walls of which are spaced from the side walls of the oil receptacle sufficiently to admit of a practically unrestricted flow of oil therebetween. Theoil within the lining is in communication with the cooling space between the lining and the oil receptacle at the top and bottom, whereby to admit of a circulation, by thermal action, of hot oil from the interior of the lining to the s ace between the lining and oil receptacle. eat willbe dissipated by the side walls of the oil rece tacle and the cooled oil will descend down t e space between the lining and receptacle and enter the space within the lining and cool the switch members therein disposed. The greater the amount of heat to ig. 4 is a plan detail of the: structure of is here shown the switch embodying my invention comprises the switch frame 10 bearing the stationary switch members 11 provided with contact'or arcing members at their lower ends,. and the movable switch members 12. Said frame is secured to the supporting structure 13 enclosing the switch operating mechanism 14. Y r a The oil-receptacle with which my invention is more particularly concerned-is formed with-the bottom wall 15 and the vertically extended side walls 16 formed of good heat conducting and dissipating material and is removably secured to the switch frame by the bolts 17 and wingv nuts 18.

The electrically insulating lining is herein formed of wood, although other well known insulating-materials may be employed, and comprises the bottom wall 20 which preferably rests uponthe bottom wall 15 of theoil receptacle, and the side walls 21 which,

in accordance with my invention, are spaced from the side walls of the oil receptacle to provide a vertical passage or cooling chamber-A down which'oil may flow to be cooled. Said side walls 21 may be secured to the bottom wall 20 by the vertically extended strips- 22 which may be carried by the bottom wall" and are dove-tailed in said side walls. Said stri s also serve as spacer strips to maintain sai passage A and support said walls 21 spaced from the side walls of the oil receptacle whereby to resist displacement upon the occurrence of pressure within the switch due to circuit interruption. I

In Fig. l the lower edge of the side walls 21'is verticallyspaced from the bottom wall whereby to provide'a lower communicating passage 23 between the passage A and the main body of oil within the oil receptacle.

' Baifle plates 24 and 25 are arranged on both sides of said passage to prevent contact of the are formed upon opening the switch; with the metallic walls of the oil -recep-tacle. Said baffle plates, however, are

so arran ed as to oppose negligible resistance to t e circulation of oil.

The side walls 21 of the electricallyinsw lating liningmay terminate a substantial distance below the surface of the oil whereby .an equivalent communicating passage equal to the height of the oil above the side walls communication with the the bottom wall 20 of the and said bottom will be provided between the main body of oil and the oil in said cooling passage A; or said side walls may extend above the surface of the oil, as in Fig. 3, and a plurality of openings 26 may beformed therethrough near the top and below the surface of. the oilto admit of communication beplurality of openings 27 therethroggh by which oil communication is establis ed between'said passage A and the main body of oil. 'A baflie plate extends above said openings and is spaced above said bottom wall to prevent access of the circuit-interrupting arc to the wall of the oil receptacle.

The hot oil within the switch and adjacent the switch members will rise to the top of the oil and enter the passage A either through the openings 26 or over the top of the lining. The relatively cool walls of the oil receptacle will dissipate the heat and cool the oil, and the cool oil'will descend in said passage and enter the space enclosed by the lining by means of the openings 23 or- 27. The cool oil willthen abstract heat through said cooling passage A;

I claim: a

1. An electric switch having an oil receptacle formed with heat absorbing and dissipating walls, stationary switch terminals extended into said receptacle and having contact-members supported by their lower ends, an electrically insulating lining disposed within said receptacle between the side walls of said receptacle and said "switch terminals, and surrounding said switch terminals and contact members, said lining relatively closely spaced from the side walls of the oil receptacle to provide an oil-cooling passage between the receptacle and lining,and having meansto provide for oil flow between the top and bottom portions of said oil-cooling passageand the top and bottom portions of the oil space within said extended into said receptacle and having contact-members supported by their lower lower portion of wall '20 is formed with a ends, an electrically insulating lining disposed within and carried by said receptacle etween the side walls of said receptacle and said switch terminals, and surrounding said switch terminals and contact members, said 5 lining relatively closely spaced from the side walls of the oil receptacle to provide an oil-cooling passage between the receptacle and lining, and having means to provide for oil flow between the top and bottom portions of said oil-cooling passa and the top 10 and bottom portions of the oi space within said lining, whereby to cool the oil in the receptacle, and means to secure the receptacle and linin removably to the switch about said switc -members. 15

In testimony whereof, I have signed my name to this specification.

TALMA T. GREENWOOD. 

